[mkgmap-dev] DEM bug at 50°N

Sun Apr 8 19:40:23 BST 2018

According to the DEM in the map, the Rhine river some 3 km away from my 
home is at an elevation of some 2600 m asl. I do not live in the Swiss 
alps, but some 50km west of Frankfurt, just north of 50°N... The correct 
elevation is about 80m.
Near Bingen (just south of 50°N), the Rhine is at an elevation of ~500m, 
somewhere between Assmannshausen and Lorch it ascends suddenly and very 
steeply to almost 3000m. In Cologne still at 500 m asl.
South of 48°N, the data seem OK; but in the north, I did not find 
reasonable values - the Elbe in Hamburg above 1000m asl.

I exclude a problem in the DEM data: before creating the map of Germany 
and Czechia, I tested with Hessen only. And then, the DEM values looked 
reasonable.

I use mkgmap 4143. The command includes parameters for DEM:
     --dem-poly=areas.poly ^
     --dem=%DEMPATH% ^
     --dem-dists=3314,4000,6000,8000,10000,15000,20000,30000 ^
areas.poly were created by splitter in the step before,
SET 
DEMPATH=E:\Maps\Development\SRTM\L32.zip,E:\Maps\Development\SRTM\M32.zip,E:\Maps\Development\SRTM\N32.zip,E:\Maps\Development\SRTM\L33.zip,E:\Maps\Development\SRTM\M33.zip,E:\Maps\Development\SRTM\N33.zip
contains DEM data from 
http://www.viewfinderpanoramas.org/Coverage%20map%20viewfinderpanoramas_org3.htm
(while testing with Hessen, %DEMPATH% was 
E:\Maps\Development\SRTM\M32.zip only which contains data from N48E006 
to N51E011).

Or is it a matter of file size? The largest *.img file has 131256kB.

Kind regards,
Bernhard